The present invention relates to an assembly for supporting anti-tip wheels on a wheelchair. More particularly, the assembly incorporates a locking mechanism which allows adjustment of the relative height of anti-tip wheels above the ground.
Some members of society have difficulty walking due to health problems. To provide mobility to these people, wheelchairs and power wheelchairs have been developed. These wheelchairs rotate forwards or backwards as torque is applied to the wheels of the wheelchair, or as the chair is accelerated or decelerated. To counter the forward or backward rotation of the wheelchair, anti-tip wheels have been combined with wheelchairs to limit the distance that the wheelchair can rotate forwards or backwards.
The height of front- or rear-mounted anti-tip wheels mounted on a wheelchair may limit the height of an obstruction which can be traversed, by causing the main wheels to be lifted off of the ground during traversal of the obstacle.
However, the greater the height of the anti-tip wheels, the greater the amount the wheelchair may rotate forwards or backwards before the anti-tip wheels engage the ground. Adjusting the anti-tip wheels to be closer to the ground alleviates this problem; however, it also limits the size of obstructions which can be overcome. The height at which the anti-tip wheels are mounted on the wheelchair, therefore, is a balance between the size of obstacles expected to be encountered and the degree of tipping one is willing to tolerate.
The present invention is an anti-tip strut assembly which allows adjustment of the height of an anti-tip wheel above the ground. A preferred embodiment of the assembly incorporates a cam mechanism to allow the initial positioning of the anti-tip wheels to be adjusted relative to the ground over which the wheelchair is expected to travel. The assembly includes an adjuster plate mounted to the strut. The adjuster plate has a pivoting connection to the strut at one end of the adjuster plate, an anti-tip wheel pin at the opposite end, and a slot between the two positions. A cam is mounted to the strut, and extends through the slot in the adjuster plate. Changes in the angle between the adjuster plate and the strut force rotation of the adjustment cam. A mechanical fastener allows the cam to be locked against the adjuster plate or the strut, preventing the cam from inadvertently rotating when an obstruction is encountered.